Transparent and conductive films (TCF) have been used extensively in recent years in applications such as touch panel displays, liquid crystal displays, electroluminescent lighting, organic light-emitting diode devices, and photovoltaic solar cells. Indium tin oxide (ITO) based transparent conductive film has been the transparent conductor-of-choice for most applications until recently due to its high conductivity, transparency, and relatively good stability. However, indium tin oxide based transparent conductive films have limitations due to the high cost of indium, the requirement of complicated and expensive vacuum deposition equipment and processes, and indium tin oxide's inherent brittleness and tendency to crack, especially when it is deposited on flexible substrates.
Two of the most important parameters for measuring the properties of transparent conductive films are total light transmittance (% T) and film surface electric conductivity. Higher light transmittance allows clear picture quality for display applications, higher efficiency for lighting and solar energy conversion applications. Lower resistivity is most desirable for most transparent conductive films applications so that power consumption can be minimized. Therefore, the higher the T/R ratio of the transparent conductive films is, the better the transparent conductive films are.T/R Ratio=(% total transmittance)/(film surface resistivity)
U.S. Patent Application Publication 2006/0257638A1 describes a transparent conductive film comprising carbon nanotubes (CNT) and vinyl chloride resin binder. The resulting transparent conductive film had T/R ratio raging from 3×10−9 to 7.05.
U.S. Patent Application Publications 2007/0074316A1 and 2008/0286447A1 describe a transparent conductive film in which silver nanowires are deposited onto a substrate to form a bare nanowire network followed by overcoating the silver nanowire network with a polymer matrix material to form a transparent conductive film. Polymer materials such as polyacrylates and carboxyl alkyl cellulose polymers are suggested as useful materials for the matrix.
U.S. Patent Application Publication 2008/0292979 describes a transparent conductive film comprising silver nanowires, or a mixture of silver nanowires and carbon nanotubes. The transparent conductive network is formed either without binder or in a photoimageable composition. The transparent and conductive films were coated on both glass and polyethylene terephthalate (PET) supports.
U.S. Patent Application Publication 2009/0130433A1 describes a transparent conductive film which is formed from coating of silver nanowires to form a network followed by overcoating with a layer of urethane acrylate binder.